This invention relates to open top gondola railway cars of depressed center design into which bulk lading is loaded and unloaded from the open top. Bulk loading is usually accomplished by "flood loading" with the car in motion and unloading is usually accomplished by rotary dumping of the car. This type of gondola car is normally employed to carry bulk materials such as coal, sand, gravel, ore or the like. Recent developments in rotary dump gondola cars have permitted a relatively low center of gravity because of the depressed center or "bathtub" design which supports the car body on stub end sills and permits the curved bottom portion of the car body to extend downwardly between the trucks with horizontal plate bottom portions extending over the trucks. These cars generally have been provided with a parabolic or a concave inner shape on the top surface of the curved bottom portion sheet when viewed in cross-section and a convex outer shape on the lower or bottom surface of the curved bottom sheet when viewed in cross-section.
An example of a railway car of this general type is shown in U.S. Pat. No. 3,713,400, issued Jan. 30, 1973, to Anthony Teoli, the inventor of the instant application. Also pertinent to the background of the invention is U.S. Pat. No. 3,817,189, issued June 18, 1974, to William Dale Bailey, and the references cited in these patents and the above-referenced parent application.
The Teoli patented car has been successful service in Canada, but is not readily adaptable to U.S. service because of the relatively small size of rotary dumping apparatus used by United States railroads and shippers. Therefore, it is necessary to design and provide shorter cars for service in the United States with existing rotary dumping equipment and with equipment of current design still to be manufactured and put into use. Such a novel design was disclosed in U.S. application Ser. No. 699,312, referenced above, of which the instant application is a continuation-in-part. The new material of this application relates to a novel stepped structure of the curved bottom portion and clearance openings in the horizontal plate portions and shear plates over the wheels whereby an increase in the clearance distance between the car and any concave or convex contoured portion of track upon which the car is located is achieved with a minimum loss of car capacity.